Methods and compositions for inducing monocyte cytotoxicity

ABSTRACT

The present disclosure relates to a new lymphokine molecule, referred to as Monocyte Cytotoxicity Inducing Factor (MCF), and its use as in cancer and other types of therapy. The disclosure further relates to the development of novel Sezary cell hybridomas which secrete MCF and thereby provide a ready source for MCF isolation and purification. Sezary&#39;s Syndrome is a leukemic proliferation of OKT4+ lymphocytes. Sezary cells were isolated by differential centrifugation and fused to CEM.8aza. r C, an HGPRTase lacking clone of CEM. The hybrid cells were studied for their ability to produce soluble mediators of human monocyte cytotoxicity. The product of a single clone, FtF3, which bore the surface phenotype of Sezary cells, was characterized. Monocyte cytotoxicity inducing factor was found to be stable at pH 2 for one hour, unlike interferon-gamma, and was found to be more heat stable as well. Moreover, treatment of MCF with antisera to interferons gamma, alpha, or a combination of gamma and alpha failed to neutralize its biologic activity. MCF binds to Matrex Gel Red A. MCF eluted from this dye-ligand was found to have an apparent molecular weight of 11,500 Daltons by gel filtration and 14,700 Daltons by SDS-polyacrylamide gel electrophoresis. (SDS-PAGE). A molecular weight of 29,000 daltons was found by use of SDS-PAGE in a second species of MCF produced under serum-free conditions.

This application is a divisional of application Ser. No. 07/417,162, filed Oct. 4,1989, now U.S. Pat. No. 5, 112,948, and a continuation-in-part of application Ser. No. 06/917,983, filed Oct. 10, 1986, now U.S. Pat. No. 4,977,245 and incorporated herein by reference.

The government may own certain rights in the present invention pursuant to Public Health Services grant NIH R23-CA39441-01.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to biological compositions and methods for inducing human monocytes to a cytoxic state. More particularly, the present invention relates to a soluble factor which induces monocyte cytotoxicity and antitumor activity.

2. Description of the Related Art

Immune protection of vertebrates is provided by a dual system that maintains two basic defenses against foreign invaders. These two defenses, termed cellular and humoral immunity, are adaptive and respond specifically to most foreign substances, although one response generally is favored. While cellular immunity is particularly effective against foreign tissue, cancer cells, intra-cellular viral infections and parasites, the humoral immune response defends primarily against the extracellular phases of bacterial and viral infections. Therefore, the cellular response is directed primarily against invading cells, while the humoral response is directed against primarily cell products, such as toxins. Moreover, whereas cellular immunity is provided by cells of the lymphoid system, humoral immunity is provided by proteins called antibodies that circulate through the fluid compartments of the body.

The dual nature of the immune system is generated from two separate populations of morphologically indistinguishable lymphoid cells called lymphocytes. While one class of lymphocytes, the T-cell lymphocytes, mediates the cellular immune response, the other class of lymphocytes, the B-cells, is responsible for the humoral immune response. Thus, when the organism is invaded by a foreign substance, for example an altered cell (e.g. viral transformed cell or tumor cell), some of the T-cells that recognize it are activated and initiate reactions that include binding to and eliminating the altered cells. On the other hand, when individual B-cells are activated, they differentiate to plasma cells that secrete specific antibodies directed against substances secreted by the foreign invader. For a good review of the foregoing, see Hood et al., Immunology, Second Edition, 1984, Benjamin/Cummings Publishing Company, Inc., Menlo Park, Calif.

While cells of B-lymphocyte lineage have found widespread clinical and industrial application in the generation of monoclonal antibodies, cells of T-lymphocyte lineage have proved of interest in part due to the numerous soluble factors they secrete. In the biologic system, T-cell factors play an important role in modulating and activating various immune functions. Isolation and characterization of various T-cell factors has been the goal of many clinical research endeavors attempting to identify those factors which might be useful in treating a number of disease states, for example, in the treatment of tumor cells and viral infectious states. Of particular interest has been the recent characterization of a factor termed T-cell growth factor, or interleukin II, which is produced and secreted by effector T_(A) cells. (See U.S. Pat. Nos. 4,401,756; 4,404,208; 4,407,945; and 4,473,642). When T_(C) cells are stimulated by interleukin II, they undergo an effector phase and are stimulated to mature into killer T-cells which are capable of identifying and eliminating various target cells. As demonstrated by the above patents, interleukin II has become an important pharmaceutical agent in the treatment of various disease states.

Optimism spurred by the preliminary success of interleukin II have lead researchers on a quest to identify other immune-mediating factors having potential clinical applicability. However, this search has generally been hampered by the existence of numerous factors secreted by the same or similar cell types. Moreover, confusion often results from the general overlapping nature of the factor activities and often times from a lack of currently available test systems for identifying individual factor activities. Without highly sensitive test systems for identifying individual factor activities, the existence of a particular factor cannot be readily distinguished from other factor activities.

Recently, interest has been shown in identifying soluble factors which serve to stimulate human monocyte cytotoxicity. Momocytes are a phagocyte of the blood which, along with macrophages and polymorphonuclear leukocytes, bind and ingest foreign substances often prior to an antibody response. “Activated” monocytes have recently been shown to exert an antitumor activity. For example, Fischer et al. (Cell. Immunol., 58:426-435 (1981)) disclose that human peripherial blood monocytes can reproducably lyse a variety of tumor cells. More recently, researchers have disclosed various factors thought to play a role in monocyte activation. For example, Kleinerman et al. (Cancer Res., 45:2058-2064 (1985)), discusses the activation of human blood monocytes by incubation with concanavalin A-stimulated lymphokine (macrophage-activating factor (MAF)), lipopolysaccharide endotoxin, and human recombinant gamma interferon. It was reported that gamma interferon, in the presence of endotoxin, was capable of activating monocyte tumoricidal activity. Moreover, MAF treatment exhibited a similar effect.

Other monocyte cytotoxicity promoting factors have been identified as; well. For example, Le et al. (J. Immunol., 131:2821-2826, 1983) has reported a T-cell hybridoma line capable of producing a macrophage activating factor with the ability to activate human blood monocytes to show enhanced cytotoxicity against a human colon adenocarcincoma line. However, this activity was found to be neutralized with specific antiserum to purified human interferon-gamma. These authors concluded that this MAF was in fact interferon-gamma.

More recently, Jones and Clouse (Immunobiol., 167: Abstract No. 365 (1984)) reported the use of lymphocytes from patients with Sezary's syndrome in the production of a human T-cell hybridoma line which is capable of producing a factor which stimulates monocyte antitumor cytotoxicity. In contrast to the factor identified by Le et al., the factor reported in the Jones and Clouse publication was not inhibited by antibodies having specificity for interferon-gaima. Although the Jones and Clouse reference did observe that two molecular weight species having the biologic activity was observable, the methodology used to identify this particular activity was not identified. Moreover, the methodology for identifying and isolating Sezary/T-cell hybridomas which secrete the particular factor was not disclosed. Clearly, not all Sezary/T-cell hybridomas are capable of producing monocyte stimulatory factors (See, e.g., Grillot-Courvalin et al., “Helper T-Hybridoina Produced By Fusion With Sezary Cells,” in: T-Cell Hybridomas, ed. by M. J. Taussig, CRC Press, Inc., Boca Raton, Fla., 1985).

It is apparent from the foregoing references that, not only are there numerous factors potentially involved in the stimulation of monocyte cytotoxicity, but additionally that these factor activities may be indistinguishable in previously available assays for detecting various cytotoxic actions.

Accordingly, the present invention is directed to methods for accomplishing the isolation of particular discrete soluble fEactors which exhibit monocyte cytotoxicity inducing activity. Moreover, the present disclosure is directed to a detailed characterization of these factors and to the preparation of T-cell hybridoma lines which produce these factors in vitro and thereby provide a ready source for isolating the factors. In that the novel factors of the present invention demonstrate a surprising ability to elicit an antitumor response by monocytes in vitro, similar to that possessed by interleukin II fo:r lymphoid cells, it is believed that these factors will provide an important new addition to the antineoplastic armament of medical science.

SUMMARY OF THE INVENTION

The present invention is directed to a composition which includes substantially purified human monocyte cytotoxicity inducing factor, also referred to herein as MCF. The composition includes a substantially purified soluble factor capable of inducing human monocytes to a cytotoxic state, the factor having a molecular weight of between about 18,100 and about 14,700 Daltons when determined by polyacrylamide gel electrophoresis under the conditions as described herein. It will be appreciated that under differing electrophoresis conditions, this molecular weight may vary.

When subjected to gel filtration chromatography, the factor has an apparent molecular weight of approximately 11,500 Daltons when chromatographed under the conditions described herein. Again, as with gel electrophoresis, it will be appreciated that gel filtration chromatography does not provide an exact molecular weight determination, rather such molecular weight determinations appear as a broad elution of monocyte cytotoxicity inducing activity, wherein the peak activity elutes from such columns at a position which corresponds to approximately 11,500 Daltons. However, this molecular weight may vary with variations in conditions, for example, running buffer, exclusion limit, column size and the particular gel filtration methodology which is utilized.

The present invention is additionally directed to a substantially purified soluble factor capable of inducing human monocytes to a cytotoxic state wherein the factor exhibits a molecular weight of about 29 kilodaltons by gel electrophoresis chromatography when the factor is obtained from cells grown in serum-free media, and a molecular weight at between about 78 and 63 kilodaltons, essentially co-eluting with bovine serum albumin by gel filtration chromatography, when grown in media containing serum. In that bovine serum albumin has a molecular weight of approximately 68,000 Daltons, it is likely the case that this higher molecular weight species of MCF has an affinity for serum albumin. This would explain why, when obtained from cells grown in the presence of serum albumin, the higher molecular weight factor exhibits a molecular weight essentially indistinguishable from that of serum albumin.

A composition which includes one or both of the above factors may be further characterized by physicochemical and biologic characteristics. For example, the composition and factor(s) retains biologic stability following treatment at pH 2 for one hour. The term biologic stability, as used herein, is defined as the retention of substantial biologic activity following the indicated treatment as defined by the present disclosure. The composition similarly retains biologic stability following treatment at 60 degrees Centigrade for one hour, and further retains biologic activity in the presence of antiserum to interferon-gamma, interferon-alpha, or a combination of antisera to interferon-alpha and gamma. MCF activated monocytes retain biological activity in the presence of antiserum to Leu-11b plus complement indicating that the factor does not appear to activate NK cells, and following treatment by the enzymes RNase, DNase and trypsin. Biologic activity is reduced following treatment by the enzyme chymotrypsin. MCF produced under serum-free conditions demonstrates charge heterogeneity, with three species having isoelectric points at 2.7, 5.6, and 6.7, respectively.

The present invention is additionally directed to a continuous cell line which produces a factor as defined by the foregoing characteristics. In particular, a continuous cell line is provided which produces a factor capable of inducing human monocytes to a cytotoxic state, wherein the cell line is produced by a process which includes the steps of immortalizing human T-cells to produce continuous cell clones; identifying a clone which produces the factor; and culturing the clone to provide the continuous cell line.

The first step of immortalizing human T-cells to produce continuous cell clones is generally defined as providing human T-cells in a manner whereby they may be cultured continuously for an indefinite period. The most convenient manner for providing such continuous cell clones is through the development of a T-cell hybridoma. T-cell hybridomas are generally well known in the art and may be generated by a variety of well known methods. In general, such methods include fusing human T-cells with a second cell population which is sensitive to growth in a selective media and culturing the fused cells in the selective media to produce the continuous cell clones. Cells may be fused in numerous ways, for example, through the use of polyethylene glycol or Sendai virus.

In a preferred embodiment, the second cell population is a T-cell lymphoma population which has been selected for growth in 8-azaguanine. By selecting for T-cell lymphomas capable of growth in 8-azaguanine, a cell population sensitive to growth in HAT selective media is obtained. Those cf skill in the art will recognize that other cell lines having other selective criteria may be utilized for fusion with human T-cells to provide the continuous cell clones. For example, additional T-cell lymphoma subtypes could be used to clone other subclasses of human T-lymphoc,ytes. Moreover, drug sensitivities and other selective criteria can be generated using other approaches including, 6-thioguanine, oubaine or oncogenic transformation. Additionally, inter-species hybrids can be generated to allow for chromosomal localization.

However, fusion is not the only means of achieving immortalized human T-cells. For example, certain human T-cells are responsive to T-cell growth factor and may be immortalized by continuous culturing in the presence of T-cell growth factor (interleukin II). Additionally, certain human T-cells, for example, certain neoplastic T-cell lines are capable of continuous growth in cell culture as are certain transformed (e.g. virus transformed) T-cell lines. While most T-lymphotrophic viruses are toxic, it is known that HTLV-1, as well as portions of the EB virus gerome, commonly utilized in B-lymphocyte transformation, can be used to transform and thereby immortalize, T-lymphocytes. All such continuously growing T-cells, and methods of providing continuously growing T-cells, are included within the scope of the present invention.

After obtaining the immortalized human T-cells in the form of continuous cell clones, a clone is identified which produces thce monocyte cytotoxicity inducing factor. The crux of the successful practice of the present invention relies on the ability to identify clones which produce this factor rather than the numerous other immune regulatory and stLmulatory factors known in the art. It is now believed that many hundreds of peptides, whose functions are unknown, are secreted by various activated T-cells. (see, e. g., Zurawski et al. (1986) Science, 232: 772-775). Moreover, depending on the particular T-cell which is immortalized, the number of clones positive for factor production may be quite low. Therefore, the assay must be not only highly specific for the present factor, but must be quite sensitive to the presence of small amounts of the factor, in order to successfully practice the present invention. Accordingly, the present disclosure is directed to an assay particularly adapted to identification of the present factor.

The final step of the present process is simply culturing the identified clone to produce the cell line. Where the immortalized human T-cell is achieved through hybridoma development, culturing will include simply culturing in an acceptable media. However, where the immortalized cell line does not involve cell fusion and instead requires the presence of a growth maintaining factor such as T-cell growth factor, culturing will require the inclusion of the particular growth factor.

In that it is believed that the factor of the present invention is secreted by a very small proportion of T-cells in general, it is a preferred embodiment of the present invention to employ Sezary cells as the T-cells to be immortalized. This is because it has been determined that a relatively large proportion of Sezary cells do in fact produce the present factor. However, in that it appears clear that not all Sezary cells produce the factor, the selection step is still required in order to identify clones producing the factor. However, if Sezary cells are unavailable, and one does not desire to screen the large number of clones which must necessarily be screened where T-cells in general are utilized, one may desire to use effector T-cells. It has been determined that a population of effector T-cells include a larger proportion of factor positive cells than do T-cells in general.

In a very general sense, the method of identifying a clone which produces the factor includes the steps of stimulating the clone with a T-cell mitogen to release lymphokines; culturing human monocytes together with appropriate target cells, for example, human cancer cells, in the presence ozf the released lymphokines; and detecting target cell lysis, wherein such lysis is indicative of the presence of human monocyte cytotoxicity inducing factor in the released lymphokines. As used herein, and as appreciated in the art, lymphokines is a generic term directed to any molecule having biologic activity for modulating the immune system. A T-cell mitogen, as will be appreciated by those of skill in the art, is a molecule or a compound having the ability to stimulate the release of lymphokines from T-cells. In a preferred aspect of the present invention, the T-cell mitogen used is phytohemagglutin, commonly referred to as PHA. However, concanavalin A ard other T-cell mitogens known to the art may be successfully utilized.

The second step of culturing human monocytes together with appropriate target cells in the presence of released lymphokines allows for the specific induction of monocyte cytotoxicity inducing factor where such factor is present in the released lymphokines. As noted previously, this particular step is quite important to the successful practice of the present invention and is disclosed in detail in connection with the disclosure of a preferred embodiment in a later section. of course, to demonstrate that the present factor is indeed effective against human target cells, an appropriate human target cell is preferred. Useful target cells have been identified as the human myeloid leukemic cell line, K562 and also HL60, L5178Y and TU5 cells. This group of tumor targets includes both NK-sensitive and NK-resistant cells. However it is believed that numerous additional cell types may be employed, for example, melanoma, lung carcinoma and bladder cell tumors.

The final step of detecting target cell lysis is conveniently performed through the use of a radioisotope which is maintained extra or intracellularly when the target cell is in a non-lysed condition, and wherein the radioisotope is released into the surrounding media when the target cell is lysed. However, it will be appreciated that additional methods known in the art, and disclosed herein, may be used.

The present invention is additionally directed to a method for generating substantially purified monocyte cytotoxicity inducing factor which includes the steps of:

(a) stimulating a continuous cell line which produces the monocyte cytotoxicity inducing factor with T-cell mitogen to release the factor into the culture supernatant;

(b) subjecting the supernatant to gel filtration chromatography;

(c) assaying chromatography fractions for human monocyte cytotoxicity inducing activity; and

(d) collecting those fractions which exhibit the activity.

Practicing the method to this extent will provide a factor containing composition which is substantially purified with respect to biologic activity as defined by the disclosed assay. However, it is believed that sufficient biologic purity may be obtained by simply passing the culture supernatant over a Matrex Gel Red A (Amicon) column in a low salt-containing buffer to bind the factor to the Matrex gel, washing the column to remove non-binding material, and eluting the bound fraction from the column with a high salt-containing buffer. Alternatively, to achieve an even more purified factor preparation, one may combine the gel filtration chromatography procedure with the Matrex gel red A column procedure. Even further purification may boe obtained by combining either or both of the foregoing procedures with a polyacrylamide gel electrophoretic separation. It has additionally been determined that isolectric focusing techniques, which are generally well known in the art, provide for purification of MCF.

In that it i; believed that the monocyte cytotoxicity inducing factor of the present invention will be clinically applicable in a manner similar to that identified for interleukin II and the various interferons, methods are additionally disclosed for clinical utilization and treatment of disease states using MCF. In addition to clinical applicability with respect to tumor treatment, as indicated by demonstrated in vitro efficacy in stimulating monocyte antitumor activity, it is believed that pharmaceutical compositions of the present invention will be useful in the treatment of infectious diseases, particularly those infectious diseases wherein the causative organisms reside in mononuclear phagocytes, for example, tuberculosis and leshmaniasis.

Additionally, it is believed that compositions included by the present invention will find diagnostic utility. Antiserum specific for MCF would be of value in determining blood levels of MCF, as well as documenting the ability of patients' mononuclear cells to produce MCF. Since MCF is produced by T-lymphocytes, and in particular, neoplastic T-lymphocytes, MCF will likely serve as a marker for diagnosis and/or evaluation of T-cell malignancies.

With respect to therapeutic utilization of MCF, one treatment protocol would include the ex vivo activation of a patient's mononuclear cells for reinfusion into the patients in a manner analogous to LAK cells as described by Rosenberg et al. (J. Natl. Cancer Inst., 75:595, 1985, and N. Eng. J. Med., 313:1485, 1985). For direct delivery of MCF to tissue macrophages, it is contemplated that MCF may be given by direct transfusion, as well as being encapsulated in liposomes. Such techniques have recently been found to increase the efficacy and significantly prolong the half-Life of related low molecular weight mediators. Liposome encapsulation can be accomplished in a number of manners, for example, as described by Fidler et al. (1976) Cancer Res., 36:3608, incorporated herein by reference.

Additionally, combination therapy employing MCF in combination with interleukin II, interferon, tumor necrosis factor and cytoxan, are contemplated. These additional agents may be obtained and employed in a manner known in the art as further disclosed herein.

It is further believed that pharmaceutical compositions which include MCF will find utility in direct infusion treatment in a manner similar to that utilized for interferon treatment. It is believed that dosage determination, as well as proper infusion techniques, is well within the Skill of the art as exemplified by Goldstein et al. (Cancer Res., 46:4315-4329, 1986), incorporated herein by reference. Moreover, in that interferons have found applicability in the treatment of various infectious disease states as noted above, it is believed that such utility will be applicable to MCF as well, for example, when employed as suggested by Nathan et al. (J. Exp. Med., 160:600-605, 1984), incorporated herein by reference.

Diagnostic procedures, utilizing antibodies specific for MCF, may be employed in a manner similar to the current clinical test for acquired immune deficiency syndrome. Most conveniently, this would include a standard enzyme linked immunosorbent assay (ELISA), well known to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Hybrid cells were adjusted to 1×10⁶/ml and stimulated with 8 ug/ml PHA(+). PHA was added back to control (−) cultures, and both supernatants harvested by centrifugation. Monocyte cytotoxicity was measured as described herein with the exception that the monocyte monolayer was incubated overnight to allow for decay of NK cell activity. The monolayer was incubated for a second 24 hr period with dilutions of MCF containing supernatants. Dilutions represented are ¼ in a total test volume of 0.2 ml. The supernatant was washed away and the ¹¹¹In-Ox-labeled targets, K562 were added (E:T,30:1). Microtiter plates were centrifuged 16 hrs later, and supernatants collected and counted. % specific release was calculated as described herein.

FIG. 2. 7.2×10³ U of MCF in 28 ml was applied to a 2.5×60 cm column of Bio-Gel P 100 equilibrated with PBS pH 7.4. The column was eluted at 1.6 ml/min and 7.5 ml fractions were collected. (°—°) MCF units/ml; (x) represent the molecular weight standards: ribonuclease A 13,700, chymotrypsinogen A 25,000, ovalbumin 45,000, and aldolase 158,000. Molecular weight determinations were calculated using Curvfit program (Interactive Microware, Inc. State College, Pa.) on an Apple II+ system.

FIG. 3. 4 ml FtF3 supernatant was passed twice over 2 ml resin bed volume and eluted with a salt gradient. 10.5 and 31.3% activity could be eluted with 1 M NaCl on Blue A and Red A, respectively. Biologic activity was not recovered using Orange A, Green A, or Blue B.

FIG. 4. 20 U of MCF/290 ug protein in 0.2 ml was mixed with sample buffer, heated, and centrifuged as described. 100 ul was loaded into each of 4 lanes of a 1.5 mm thick 10% polyacrylamide-SDS gel. After running at 200 V for 4 hrs, the gel was cut into 1 cm slices, crushed, eluted, aind bioassayed. Companion lanes were stained by both Coomassie Blue and silver method. Molecular weight standards used were phosphorylase beta (94,000), bovine serum albumin (67,000), ovalbumin (43,000), carbonic anhydrase (30,000), soybean trypsin inhibitor (20,000), and α-lactalbumin (14,400). Molecular weight determinations were made using Ferguson plot analysis.

FIG. 5. FtF3 cells were incubated 4 h with various doses of actinomycin D. Cells were washed and stimulated with PHA for 24 h before harvesting supernatants by centrifugation, extensive dialysis, and bioassay.(▪) One set of each dose of inhibitor-treated cells was labelled with ³H-uridine, stimulated, lysed and harvested 24 h later, and counted by liquid scintillation.(□) Viability of FtF3 at 24 h was greater than 80% at all doses tested.

FIG. 6. FtF3 cells were incubated 4 h with various doses of cyclohex:imide. Cells were washed and stimulated with PHA for 24 h before harvesting supernatants by centrifugation, extensive dialysis, and bioassay.(▪) One set of each dose of inhibitor-treated cells was labelled with ³H-amino acids, stimulated, TCA-precipitated 24 h later, and counted by liquid scintillation.(□) Viability of FtF3 at 24 h was greater than 80% at all doses tested.

FIG. 7. FtF3 cells were incubated 4 h with various doses of puromycin. Cells were washed and resuspended either with (▪) or without (□) PHA, and incubated 24 h before harvesting supernatants by centrifugation, extensive dialysis, and bioassay. Viability of FtF3 at 24 h was greater than 80% at all doses tested.

FIG. 8A. Biological activity and 15% SDS-PAGE.(▪) Low molecular weight standards (BRL, Gaithersburg, Md., U.S.A.) used were ovalbumin, (43K), alpha chymotrypsinogen (25.7K), beta-lactoglobulin (18.4K), lysozyme (14.3K), bovine trypsin inhibitor (6.2K), and insulin A and B chain (2.3K and 3.4K).

FIG. 8B. 15% SDS-PAGE: Western blot. Solubilization buffer (A); MCF purified over Matrex Gel Red A (B); low molecular weight standards, BRL (C): stained with colloidal gold (Aurodye).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Introduction

Concepts of monocyte activation for cytotoxicity have undergone a change from the “all or none” paradigm to the more precise concept of a discrete stepwise process. Our present understanding of monocyte activation has been addressed by Cohn (Jrnl. Immunol., 121:813-816, 1978). Moreover it is generally recognized that activation is regulated by products of T-lymphocytes. Soluble mediators of mononuclear phagocyte activation have recently been reviewed by Nathan et al., supra.

From these studies and earlier reports, interferon gamma would appear to the most important if not the only regulator of cytotoxicity against microorganisms and has recently been identified as a migration inhibitory factor. However, other studies have suggested that colony stimulating factor (CSIF I), and the interferons alpha and beta, may have roles in regulating secretory or proliferative functions. The present invention is directed to the perhaps surprising discovery that an additional factor, termed monocyte cytotoxicity inducing factor (MCF) by the present inventors also plays a role. In light of the present finding, it is likely that additional factors will be identified through the development of the individual assays particularly suited to identification of factor activities.

The MCF disclosed by the present invention is characterized biologically by an ability to stimulate monocytes to a cytotoxic antitumor state. While the precise function of MCF within the biologic system is unknown, it is believed that it might play a role in affording specific activation of the cellular immune system. MCF appears to cause an increase in the synthesis and release of IL 1 by monocytes, which may act to either perpetuate the cytolytic state, to directly lyse susceptible tumor targets, or to induce cytostasis. MCF has no TNF, m-CSF, or IFN-like anti-viral activity. Similarly MCF has no activity when tested in the IL 1, IL 2, or m-CSF assays. Moreoever, MCF was not directly cytotoxic for the targets K562 or L929, indicating that MCF has no lymphotoxin-like activity of its own. The factor is characterizable as having two molecular weight forms, one about 29,000 Daltons, and a lower molecular weight form of between 11,500 and 18,100 Daltons, depending on the particular molecular weight determination method utilized. It is emphasized that these two molecular weight forms exhibit indistinguishable biologic activity in terms of monocyte activation. Therefore, the term MCF is meant to relate to either of these two molecular weight forms individually or in combination.

Sensitivity of MCF to the enzymes and metabolic inhibitors described herein are consistent with a conclusion that MCF is a peptide. For example, responses to metabolic inhibitors (actinomycin-D, puromycin, and cycloheximide), suggest that transcription of message is necessary and that: messenger RNA for MCF does not persist. Because treatment of non-lectin-treated cells with puromycin did lead to production of MCF, and because total suppression of MCI could not be achieved with cycloheximide and puromycin, these data are consistent with either regulation of transcription by a repressor protein or its product, or at the level of translation, by stabilization of message.

MCF is most conveniently isolated through the preparation of a T-cell hybridoma employing Sezary cells isolated from an individual having Sezary's syndrome. Sezary's syndrome is characterized by a proliferation of leukemic helper T-cells, and is discussed in some detail by Broder et al. (J. Clin. Invest., 58:1297-1306, 1976). Sezary's cells circulate in the peripheral blood and are known to provide T-cell help for immunoglobulin production. These cells are identified by their characteristic cerebriform nuclei, PAS positive vacuoles, and additionally by their surface marker phenotype (OKT3+, OKT4+, OKT8−, OKIal−(+)). Helper function has been defined by the ability of Sezary cells to stimulate polyclonal IgG production by B lymphocytes and by their production of MIF. Although lymphokine production does not necessarily segregate exclusively to any one subclass of T cells, Sezary's cells most probably represent a homogeneous clonal expression of one particular subclass of human T-lymphocytes which can be studied for production of lymphokine mediators uncontaminated by other T-cells.

The use of Sezary cells, as noted above, is not crucial to the practice of the present invention in that it is believed that MCF production is a feature common to lymphocyte populations in general. However, not all cells of a particular T-cell population produce MCF. Thus, where a general T-cell population is utilized, only a very small percentage of cells are likely to produce MCF. In the case of Sezary's cells, it appears as though MCF production is a more generalized phenomenon. Therefore, Sezary's cells are preferred in that T-cell hybridomas produced from Sezary's cells provide clones wherein there is a much greater likelihood that any one particular clone would produce MCF Conversely, it is likely that when general T-cell populations are employed for hybridoma production, a substantial number of clones will likely have to be screened before a positive clone is identified. However, where Sezary's cells are not available, one may employ helper T-cells, in that it appears that helper T-cell populations contain a sufficient percentage of positive cells to avoid the exhaustive screening which would be necessitated by employing general T-cell lymphocyte populations.

Recently, strong evidence has been presented that interferon-gamma is the major mediator of macrophage/monocyte activation, and may be identical with the lymphokine macrophage activation factor (MAF). Interferon-gamma has also been described as the mediator of inhibition of mononuclear phagocyte migration and hence may be migration inhibition factor (MIF). However, it is known that activated Factor B of the alternative complement pathway (Bb), plasminogen activator (PA), and other products of monocytes will inhibit migration. Nathan et al., supra, have recently reviewed the range of mediators of mononuclear phagocyte activation.

The production of lymphokines by malignant T-cells is important in understanding host defense in conditions with chronic courses such as Sezary's syndrome and may reflect production of such mediators by non-malignant counterparts in the normal host. In developing the present invention, attempts were made to expand Sezary cells with interleukin II (IL-2), but these attempts were unsuccessful. Similar results have been reported by other groups, and have been attributed to the lack of IL-2 receptor expression or proliferation of sezary cells by non-IL-2 dependent means. Clearly, as additional cell lines are screened for MCF production, cells will be identified which may be immortalized through the inclusion of growth factors in the cell growth medium, thus avoiding the need for hybridoma development.

Previously, hybridization has been utilized to perpetuate subclasses of murine T-cells and this technique was applied to Sezary's cells for the present invention. Other groups have employed Sezary cell hybridomas to study BCGF (B-cell growth factor) production by Sezary's cells. In the present invention, six cell lines were obtained by hybridization and all were capable of inducing human blood monocytes to become cytotoxic for the myeloid leukemia target, K562. For further study, one hybrid, FtF3, was selected whose phenotype (OKT3+, 4+, 8−, OKII1−, sIgG−) was identical to the parent Sezary's cell. It is of interest that all lines produced a lymphokine capable of inducing monocyte cytotoxicity (MCF). This probably results from positive selection of fusion partners since similar hybridization experience using whole murine T-cell populations have given rise to much smaller percentages of clones with MAF-like function.

Supernatants from PHA-stimulated FtF3 induced human mononuclear cytotoxicity but contained no detectable-interferon. Antisera to native interferon-gamma when added in excess to MCF having no antiviral activity produced only a 10-15% decrease in specific lysis of the target K562. Moreover, when formal titrations of the anti-IFN-gamma antisera were carried out using the constant antibody method previously described as being optimal for the detection of cross-reactivity with IFN-gamma, no neutralization titer could be determined. In contrast, treatment with the antisera to interferon-alpha caused a small increase in specific release. Addition of both antisera together produced no change in specific lysis. Both antisera were produced against partially purified native human interferons. In the case of the antisera to interferon-gamma, some cross-reactivity may be detected in that an MCF-like molecule could have been present in the preparation used to raise the antisera which was previously not recognized.

Recently, Schreiber has described the development of a series of monoclonal antibodies which are capable of differentially blocking antiviral or MAF activity of interferon-gamma, respectively. In particular, monoclonal antibodies directed against the C-terminus of recombinant interferon-gamma were reported to block MAF but not the antiviral activity of the recombinant interferon-gamma, while the antibodies to the N-terminus of recombinant interferon-gamma blocked antiviral but not MAF activity. Therefore, these findings could be consistant with an interpretation that MCF was an altered interferon species produced by a T-cell leukemia-derived hybridoma. However, the fact that MCF has recently been determined by the present inventors to be produced by normal effector T-cells, appears to rebut this theory.

These issues were further approached by direct comparison of the physicochemical properties of MCF and native interferon-gamma. Unlike interferon-gamma, MCF was stable at pH 2 but: was partially inactivated at pH 8 and was much more stable than interferon-gamma. IFN- was inactivated by trypsin, in contrast to the effect of this enzyme on MCF. These findings would support the concept that MCF is not an altered interferon-gamma which has lost antiviral, but not MAF activity, because interferon-gamma lost both MCF and antiviral activity with both low pH and heat treatment.

MCF is a lymphokine distinct from TNF, IL 1, IL 2, m-CSF or IFN. MCF has no activity when tested in assays for IL 1, IL 2 or m-CSF. MCF had no TNF, m-CSF, or IFN-like antiviral biological activity when compared to rTNF, purified human m-CSF, IFN gamma or alpha/beta, respectively. In addition, MCF had no cross reactivity with m-CSF in the radioimmunoassay for m-CSF.

Gel filtration chromatography of concentrated supernatants from cells raised in the presence of serum, revealed two molecular weight species, one with a molecular weight of 64,000 daltons which co-eluted with the major protein peak, bovine serum albumin, and a second with a molecular weight of 11,500 daltons. Although yields from our Bio-Gel P-100 column have been low, these values differ from the molecular weight of 50,000 reported for native human interferon-gamma when chromatographed under similar conditions. When such cells were cultured in serum-free media, the higher molecular weight species migrates at about 29 kD upon SDS gel electrophoresis

MCF was found to bind to Matrex Gel Red A (procion-red agarose; Amicon) and eluted with 1-N NaCl. Similar results have been reported for native interferon-gamma. MCF eluted from Matrex Gel Red A was electrophoresed under reducing conditions on a 15% SDS-PAGE gel. Two molecular weight species were identified. The first had a molecular weight between 25,000 to 28,000 daltons when produced in serum-free media and the second had a molecular weight of about 14,700 Daltons. The specific activity was 610 MCF units/mg protein and 1350 MCF units/mg protein, respectively. Yields from this procedure have been excellent with recoveries greater than 90%, despite treatment with SDS.

Electrophoresis under reducing conditions followed by dialysis to remove SDS has resulted in each case in a diminution of biologic activity associated with the higher molecular weight form and greater recovery of the lower molecular weight form.

The following methods describe the preferred embodiment employing Sezary cells from two patients identified as having the syndrome. To achieve an immortalized Sezary cell line in the form of a Sezary/T-cell hybridoma, Sezary cells were fused with a T-cell lymphoma line conditioned in a manner to be sensitive to HAT selective media. The resulting hybridomas were found to produce MCF and were capable of being Continuously cultivated. Culture supernatants were found to contain sufficient quantities of the MCF to allow for substantial purification through the utilization of techniques described herein.

EXAMPLES 1. Isolation of Sezary's Cells

Mononuclear cells were isolated from 60 ml whole blood from a patient previously known to have Sezary's syndrome. Mononuclear cells were isolated by centrifugation over Ficoll-Hypaque (Pharmacia, Piscataway, N.J.). 7.5×10⁷ cells having a phenotype of 87% OKT 3+, 77% OKT 4+, and 12% OKT 8+ were recovered from the F/P centrifugation and applied to a 35 ml gradient of Percoll (Pharmacia) according to the method of Gemlig-Meyling and Waldman (J. Immunol. Method., 33:1, 1980, incorporated herein by reference). Briefly, the gradients were made by mixing 168 ml Percoll with 144 ml 2×PBS, and centrifuged for 40 min at 21,000×g in a Beckman Model 71 centrifuge with a SS-34 fixed angle rotor. The cells were suspended in 5 ml of Hank's balanced salt solution (HBSS), layered gently on the gradient, centrifuged at 100×g for 20 min at 20° C. in a swinging bucket rotor. Standard density marker beads (Pharmacia) were loaded on a companion gradient.

Three distinct “bands” were recovered from Percoll. At the interface between the Percoll and sample were 1.5×10⁶ cells, the majority of which were polymorphonuclear leukocytes, and were discarded. Band I, 2 cm below the interface contained 1.9×10⁷ cells which when studied by flow microfluorometry (FMF) were 90.2% OKT 3+, 80% OKT 4+, and 47% OKT 8+, and were morphologically small lymphocytes. Band II, located 5 cm below the interface contained 7.8×10⁶ cells, which were 97% OKT 3+, 96% OKT 4+, and 17% OKT 8+. Microscopically, these cells were larger and had cerebriform nuclei. 38% of the total cells applied to the gradient were recovered.

Cells isolateid in Band II were washed and resuspended at 5×10⁵ cells/ml in RPMI 1640 with 10% fetal calf serum (FCS). Aliquots of these cells were cultured with 10 units/ml final concentration of interleukin II from the Gibbon ape cell line NLA-144. These cells failed to divide or incorporate 3H-Tdr after 72 hrs of culture thus demonstrating a lack of IL-2 responsiveness.

2. Preparation of 8-azaguanine Resistant T-lymphocytes

Since these particular Sezary's cells were not capable of indefinite sustained growth in tissue culture, it was decided to prepare a continuous T-cell hybridoma line by fusing the Sezary's cells with a T-lymphocyte population which has been conditioned to grow continuously in tissue culture. To achieve hybrid selectability, it was first necessary to select a cell population which was sensitive to HAT selection medium. This was accomplished through the preparation of an 8-azaguanine-resistant T-lymphocyte population.

It has been determined that certain commercially available T-lymphocyte cell lines are to be preferred over others. CCRF-CEM is a cell line obtainable from the ATCC which, due to its apparent genetic stability, is to be preferred in generating hybridomas of the present invention. Two additional cell lines, MOLT and Jurkat, have been found to be genetically unstable upon drug selection and therefore unsuitable. However, the techniques of the present invention are applicable to any genetically stable T-cell lymphocyte or other cell type which can form a stable fusion product with T-cells and which is capable of continuous growth in culture. Determination of the foregoing criteria is within the skill of the art and the scope of the present disclosure is not limited to the preferred embodiment employing CCRF-CEM.

To generate 8-azaguanine resistant CCRF-CEM, cells were obtained from the American Type Culture Collection and grown in RPMI 1640 with 10% FCS. CEM was grown in increasing concentrations of 8-azaguanine primarily according to the method of Okada (Proc. Natl. Acad. Sci., 78:7717, 1981, incorporated herein by reference). However, beginning with a concentration of 2 uM, the dose was doubled every 2 days until a dose of 16 uM was reached at which time the dose was doubled every 10 days until a dose of 100 uM was reached. After 6 weeks the cells were recloned and tested for their ability to grow in HAT-containing media (hypoxanthine, aminopterin, and thymidine), and subjected to flow microfluorometry.

3. Generation of T-cell Hybridomas

T-cell hybriclomas were formed between Sezary cells, isolated as described in section 1 above, and the 8-azaguanine-resistant, HAT-sensitive CEM T-lymphocyte line (CEM.8aza.^(r)C), prepared as described in section 2 above. In particular, 7.5×10⁶ cells from Band II of the Percoll gradient fractionation of patient's mononuclear cells were subjected to flow microfluorometry and light microscopic examination. These cells were hybridized to an equal number of CEM.8aza.^(r)C using polyethylene glycol (mol wt 1000, Sigma, St. Louis, Mo.) as described by Jones, C. M., “T-cell Hybridomas Producing Macrophage Activation Factors,” In: T. Cell Hybridomas, Ed.: M. Taussig, CRC Press., Inc., Boca Raton, Fla., 1985, pp. 56-68, incorporated herein by reference. The fused cells were cultured for 24 hrs in RPMI 1640 with 10% FCS prior to addition of HAT-containing medium (hypoxanthine 1×10⁻⁴M, aminopterin 4×10⁻⁵ M, and thymidine 1.6×10⁻⁵ M). Colonies were selected after 1 month in HAT media and cloned by limiting dilution.

Individual hybridoma clone colonies which were isolated by this procedure were adjusted to a culture density of 5×10 ⁵ cells/ml and stimulated with 16 ug/ml phytohemagglutinin (PHA; Miles-Yeda, Rehovot, Israel) for 24 hours to stimulate lymphokine production. Thus, hybridoma clones were screened for positive MCF production by mitogen stimulation followed by subjecting the resultant hybridoma supernatants to biologic screening in the human monocyte cytotoxicity assay, which is discussed in detail below.

The human T-cell hybridoma was also successfully maintained in 5% Eetal calf serum (FCS), then grown in serum free media for at least 24 hours after stimulation by phytohemogglutinin (PHA). Either tissue culture media not supplemented by serum, or a serum-free media described by Sachs, L. (1975) Clin. Exp. Immunol. 33:495 and incorporated-herein by reference, will support this growth for a limited time span. This cell growth procedure permits analysis of MCF prepared in serum-free conditions.

In particular, supernatants of stimulated and unstimulated clones were incubated 20 hours with the monocyte monolayer. Serial dilutions of the supernatant were made to quantitate MCF in each sample. The data in FIG. 1 show that all six clones produce a factor(s) which induces human monocytes to kill K562. Their phenotypes were studied by FMF and two clones, FtF3 and FtA5, were uniformly OKT 3+, 4+, and were OKT 8− and OKMT 1−, and IgG−.

Table 1 demonstrates the results obtained when supernatants from two representative MCF-producing hybridomas, FtA5 and FtF3, were subjected to the in vitro monocyte cytotoxicity assay. Cytotoxicity was measured by adding a fixed input of supernatant (25, 50 and 100 vi.) to a total test volume of 0.2 ml.

TABLE I Specific Cytotoxicity Induced By Hybridoma Supernatants Hybrid Input (ul) % Specific Lysis FtA5 25 10.3 50 25.1 ± 6.9 100 38.3 ± 8.4 FtF3 25 11.1 50 26.2 ± 10.4 100 37.7 ± 6.8

4. Human Monocyte Cytotoxicity Assay

As noted above, successful practice of the present invention rests on the ability to successfully identify MCF activity in an in vitro assay which has been designed to distinguish MCFP activity from the numerous other lymphokine activities produced by T-cells. The assay described below has been derived in part from an assay method reported by Koren and his associates (Fischer et al., Cell Immunol., 58:426, 1981). However, the assay as described in the Fischer et al. reference was found to be unacceptable in that it is not designed to measure lymphokine induced cytotoxicity and does not eliminate natural killer cell activity. It, therefore, must be modified as followqs.

Human monocyte enriched leukopaks were obtained as a byproduct of the platelet donor program at M. D. Anderson Hospital, and were prepared with an IBM Model 2997 Cell Separator. Only healthy volunteer donors were used. All volunteer donor; signed an informed consent, and the protocol was approved by the Committee for the Protection of Human Subjects, University of Texas Health Science Center. Mononuclear cells were prepared by centrifugation over Ficoll/Hypaque. Monocyte monolayers were prepared by adherence to 96-well flatbottom plates previously coated with human serum as described by Golightly et al. (Blood, 61:390, 1983, incorporated herein by reference), and allowed to adhere to the serum coated plates for 15-30 mins followed by vigorous washing with warm (37° C. ) Hank's balanced salt solution. This resulted in a confluent monolayer of >95% esterase positive cells. The monolayer was incubated overnight to allow for decay of residual natural killer activity before addition of lymphokine preparations on clay 2. The monolayers were incubated with lymphokine for 20 hrs, washed, and the ¹¹¹In-Ox labeled K562 added as targets.

The ¹¹¹In-Ox labeled K562 target cells were prepared by the method of Wiltrout et al. (in: Manual of Macrophage Methodology, Ed. H. B. Herscowitz et al., Marcel Dekker, Inc., N.Y., 1981, pp 337-344, incorporated herein by reference). The effector to target ratio was 30:1. Spontaneous release averaged 15% (7-20%) in greater than 50 experiments. LPS (Lipopolysaccharide) free RPMI 1640 (M. A. Bioproducts, Walkersville, Md.) with 10% heat-inactivated AB-negative human serum (FLOW Laboratories, Arlington, Va.) was used throughout the assay procedure. After 18 hrs incubation of monocyte monolayer with target, the plates were centrifuged and supernatant was removed and cpms were counted in a Beckman Biogamma 2000. Specific release was calulated as described by Wiltrout, supra. Units of MCF activity were calculated as described by Lohmann-Matthes (Kniep et al. (1981), J. Immunol., 127:417). 20% specific release equals 1 unit of MCF. Other tumor targets used were HL-60, L5178Y and TU5 (Table V).

The primary distinction between the present assay and the one described by Fischer et al., is the finding that it is absolutely crucial that LPS-free media be utilized in order to distinguish the MCF activity from interfering activities. For the particular activity investigated by Fischer et al., the use of LPS-free media was not crucial in that it is noted by those authors that similar activities were observed regardless of whether LPS-free media was utilized. However, with respect to MCF, when LPS-containing media is used, a spontaneous release of label occurs and induction of lymphokine (MCF) directed cytotoxicity cannot be measured.

5. Deposit of Representative Sezary Cell Hybridomas with the American Type Culture Collection

By the foregoing procedures, six hybridoma clones were identified whose supernatants exhibited MCF activity. Two were chosen for further physiochemical and biologic characterization. It has been determined that those two hybridomas, designated Ft.A5 and Ft.F3, both secrete the same MCF biologic profile, as determined by the characterization criteria disclosed herein. Accordingly, one of these hybridomas, Ft.F3, has been deposited with the ATCC 10801 University Boulevard, Manassas, Va. 20110 and accorded ATCC reference number HB9713.

6. Characterization of MCF A. MCF is Antigenically Distinct From Interferon Gamma

1) Generation of MCF

MCF was generated by stimulating 5×10⁵, 1×10⁶, 2.5×10⁶, or 5×10⁶ FtF3 or FtA5 cells/ml with 2, 4, 8, 16, or 32 ug/ml PFIA (Miles-Yeda, Rehovot, Israel) in RPMI 1640 with 1, 2.5, 5, or 10% FCS (Hyclone, Sterile Systems, Logan, Utah) for 24, 48, or 72 hrs. Unstimulated controls were grown with each to which an equal amount of PHA was added at the end of incubation. The cells were centrifuged, and the supernatants filter-sterilized, and stored at −30° C. . For characterization and purification, MCF was then prepared by stimulating 1×10⁶ cells/ml in RPMI 1640, 1% FCS with 8 ug/ml PHA for 24 hrs, centrifuged, and filter sterilized. This routinely gave approximately 40 U/ml activity. Unstimulated controls to which PHA was added back were used in all experiments.

MCF was also generated in serum-free media. FtF3 cells were first grown in RPMI 1640 containing 5% FCS. Cells were then washed twice with Hanks balanced salt solution (HBSS) and once with RPMI 1640. Cells were resuspended at a concentration of 1×10⁶/ml or 3×10⁶/ml in either RPMI 1640 containing 10, 5, 1, or 0.1% heat-inactivated, AB-negative human serum, RPMI 1640 alone, or a serum-free media described by Sachs (Clin. Exp. Immunol., 33:495, 1978, incorporated herein by reference). Phytohemogglutinin (PHA) was added to a final concentration of 0, 0.5, 1.0, 2.0 or 4.0 micrograms/ml. Supernatants were collected at 24 and 48 hours, filter sterilized, and stored at −70° C. Satisfactory growth could only be maintained in RPMI 1640 having at least 5% fetal calf serum. However, after FtF3 had been conditioned to grow in media having 5% FCS, this cell line was capable of producing MCF under serum-free conditions as described herein. The total units of MCF recovered were scarcely different among the serum-containing medias or RPMI alone. The serum-free media of Sachs resulted in a decrease in MCF production of 5 to 10 U/ml. In addition, an increase in cell concentration from 1×10⁶ cells/ml to 3×10⁶ cells/ml did not increase levels of MCF production which is likely the result of decreased viability at higher cell density.

2) Interferon Assay

Human interferon activity was measured as inhibition of plaque formation by Sindbis virus on WISH cells as described by Baron et al. (Infect. Immun., 32:449, 1981). Sindbis virus, human alpha, beta, and gamma interferons were prepared by Drs. Samuel Baron and Marlyn Langford, University of Texas Medical Branch, Galveston, Tex. WISH cells were obtained from Drs. Baron and Langford. Using this plaque inhibition assay, interferon was not demonstrated in supernatants of FtF3 and FtA5.

3) Treatment of IFN-gamma and MCF With Antisera to Various Interferons

Antibody to a partially purified preparation of native human gamma interferon (Langford et al. (1981), J. Immunol., 126:1620), a 20 peptide N-terminal fragment of recombinant gamma interferon (Johnson et al. (1982), J. Immunol., 129:2357) and human alpha interferon (Langford et al., supra) were prepared as described in the referenced articles. In initial experiments, 40 Units of MCF or 100 U IFN-gamma in 1 ml RPMI 1640, 1% FCS were incubated with 100 U of each of the antisera above alone or in combination at 4° C. for 30 min, 1 hr, and 4 hr. Following this incubation, serial dilutions of the IFN or MCF were made in RPMI 1640, 10%FCS and residual macrophage activating factor activity measured in the MCF assay.

27 U/ml of partially purified MCF were diluted ½ (13.5 U), ¼ (6.7,5 U), and ⅛ (3.375 U). Serial half-log dilutions were made of these dilute MCF, and the predicted number of units were confirmed by measurement in the MCF bioassay. Next, 27 U/ml of partially purified MCF were subject to serial half-log dilutions up to a final dilution of ⅛. 100 U, 50 U, or 25 U of each of the anti-IFN-gamma, antisera was added to each of these MCF dilutions and incubated for 1 hr at 25° C. Residual MCF activity was calculated in the constant antibody titration as recommended by Kawade (J. Ifn. Res., 4:571-584, 1984). Units are expressed as described by Lohmann-Matthes (Kniep et al., supra).

Results from two representative sets of experiments are summarized in Table II. Anti-interferon-alpha produced no significant change in % specific release. On the contrary, the presence of this antisera during the activation has consistently produced small increases in specific lysis. The antibody to a partially purified preparation of native human interferon-gamma (SEA-activated human PBL) produced a decrease of only 15% and 10% specific lysis. Antisera to the 20-peptide N-terminal fragment of recombinant interferon-gamma or to a combination of interferons alpha and gamma failed to neutralize MCF. The antisera themselves produced only small changes in spontaneous release of label Erom the target K562 when added in place of the activating agent (spontaneous release=22.6% with media and monocytes alone; specific release=−13.2% with anti-IFN-alpha, =4.66% with anti-IFN-gamma native, and =8.4% with anti-IFN-gamma N-terminus.) More importantly, IFN-gamma in amounts up to 1000 U/ml final concentration increased specific lysis only 6.2%. Because IFN-gamma did not produce significant activation for cytotoxicity in the present assay, direct comparison with MCF could not be performed.

TABLE II Treatment of MCF with Antisera % Specific Lysis Treatment Exp 1 Exp 2 untreated 54.6 ± 3.8 29.8 ± 5.4 anti-IFN-alpha 57.6 ± 5.0 35.8 ± 4.2 anti-IFN-gamma (native) 40.6 ± 3.8 19.9 ± 8.5 anti-IFN-gamma N-terminus 26.5 ± 8.0 anti-IFN-gamma (native) + 48.8 ± 5.3 anti-IFN-alpha

In order to confirm that increasing concentrations of antibody relative to MCF units would not affect induction of cytotoxicity, the following experiments were performed. Serial checkerboard dilutions of 27 U/ml partially purified MCF were carried out as described above. In each experiment, 100, 50, or 25 U of the anti-IFN-gamma anti-bodies were added separately to MCF dilutions and residual MCF units were measured. The results summarized in Table III demonstrate thLat 100 U anti-IFN-gamma native reduced total bioassayable units by 7 U/ml. This is consistant with preceding experiments. Addition of 50 U/ml anti-IFN-gamma (native) and all inputs of anti-IFN-gamma N-terminus caused an increase in bioassayable units.

TABLE III Treatment of MCF with Anti-IFN-gamma by the Constant Antibody Technique MCF (units/ml) Input Ab (U/ml) anti-IFNgamma (native) anti-IFNgamma-N-terminus 0 27 27 25 28 39 50 58 46 100 20 40

FtF3 and FtA5 MCF were also capable of activating murine peritoneal exudate macrophages for cytotoxicity against the target L5178Y. The presence of LPS did not appear to augment cytotoxicity induced by these lymphokines.

B. MCP is Distinct from IL 1, IL 2, TNF and m-CSF

1) Measurement of IL 1, IL 2, TNF and CSF Biologic Activity

IL 1 activity was measured using the D10.G4.1. cell line as described by Kaye and Janeway (J. Immunol. 133, 2291, 1984). IL 2 activity was measured as described by Bonnard, using cultured human T-cells (Cell. Immunol. 51:390, 1980). TNF activity was measured by direct cytotoxicity against L929 cells as described by Gately and Mayer (J. Immunol. 116:669, 1976). M-CSF was measured by both murine bone marrow colony formation (Waheed and Shadduck, Exp. Hematol. (1989) Exp. Hematol., 17:61-65 (Shadduck and Waheed, (1989) Ann. N.Y. Acad. Sci., 554:156-166, and by radioimmunoassay specific for purified human m-CSF.

2) Addition of Lymphokines to MCF Assay

Purified human IL 1 (alpha plus beta), rIL 1a, rIL 1b, (Cistron Biotechnology, Pinebrook, N.J., USA), rIL 2 (Genzyme Corp., Boston, Mass., USA), rGM-CSF, or purified m-CSF (Waheed and Shadduck, supra), was added to the human monocyte cytotoxicity assay in order to determine the ability of lymphokines other than MCF to activate monocytes for tumor cytotoxicity. Antibody to a partially purified preparation of native human IFN-gamma, a 20 peptide n-terminal fragment of rIFN-gamma, and human IFN-alpha were used, and neutralization was carried out using the constant antibody method as previously described by Jones et al. (J. Immunol. 137:571, 1986). Anti-serum to purified m-CSF, capable of neutralizing 0, 1,00 and 1,000 units/ml was added to a preparation of human MCF containing 33 U/ml. These were incubated one hour at room temperature. Resultant supernatants were tested in the MCF biologic assay.

Using K562 as a cytotoxicity assay as previously determined, IFN-alpha/beta had no, and IFN-gamma only slight activity. Neither IL 1 or IL 2 had any activity in the MCF assay. Anti-sera to m-CSF failed to neutralize MCF activity. The CSF's had effects different from MCF. They caused monocyte cell division, altering the effector to target ratio and causing cells to assume a rounded morphology. MCFs by contrast did not cause cell division, out induced cytotoxicity and caused the cells to assume a macrophage-like morphology. The details of the effects of cytokines or lymphokines other than MCF, in the MCF assay, are shown Table IV.

TABLE IV Effect of other cytokines in the MCF assay Cytokine U/ml % specific lysis MCF U/ml Specific antisera treatment of MCF IFN-α 1000 −8.9 ± 8.8 18.1 ± 2.6 αIFN-αinput Exp. 1 Exp. 2 100  −2.1 ± 12.4 % specific lysis 10 −5.4 ± 9.2 0 U/ml 54.6 + 3.8 29.8 + 5.4 1  4.5 ± 3.0 100  57.6 + 5.0 35.8 + 4.2 αIFN-γ input Native N-terminus U/ml U/ml IFN-γ 1000  6.2 ± 4.4 40.0 ± 2.9 0 27 27 100  3.4 ± 3.2 25 28 39 10 −3.5 ± 1.1 50 58 46 1 −2.2 ± 1.9 100 20 40 rIL1α 10 −0.7 ± 7.6 24.4 ± 6.5 1 −3.6 ± 5.6 0.1 −4.1 ± 4.1 rIL1β 10 −1.8 ± 9.6 24.4 + 6.5 1 −4.9 ± 4.6 0.1 −8.7 ± 2.8 pIL1(α + β) 100 −10.2 ± 4.0  18.1 ± 2.6 10 −5.2 ± 2.7 1 −5.4 ± 7.9 0.1 −10.9 ± 3.3  rIL2 1000  2.7 ± 6.2 20.0 ± 2.0 100 −3.2 ± 3.5 10 −4.6 ± 4.3 1 −10.2 ± 17.7 GM-CSF 200 −0.6 ± 4.9 20.0 ± 4.4 100  5.7 ± 3.1 50  −2.5 ± 15.9 am-CSF input MCF activity U/ml U/ml m-CSF 1730 −3.9 ± 4.7 50.0 ± 3.9 0 33.3 173 14.5 ± 4.6 100 40.0 17.3 26.0 ± 7.5 1000 50.0 Various cytokines were added to the MCF bioassay. Specific antisera were added to MCF-containing supernatants to determine whether any MCF activity could be neutralized by antisera to other cytokines.

3) MCF is Distinct from Natural Killer Cells (NK)

In order to remove human NK cells from whole human peripheral blood mononuclear cells, anti-Leu-11B was used (Becton Dickinson, Mountain View, Calif., USA) (Itoh et al., J. Immunol. 134:802, 1985). Human monocyte monolayers were treated with anti-Leu-11B and subjected to either activation with MCF for measurement of cytotoxicity, or staining with trypan blue for v:Lability. Human monocyte monolayers treated with anti-Leu-11B plus complement and activated with MCF did not diminLsh MCF mediated cytolysis, nor was viability at the ionocyte monolayers decreased when compared to control monolayrers. Monocyte monolayers were activated with either crude MCF (23.8 U/ml) or MCF prepared by Matrex Gel Red A chromatography (83.3 U/ml). Cytotoxicity was measured using K5S2, HL60, L5178Y or TU5. Specific release of MCF was comparable with both NK-sensitive and NK-resistant (TU5 and L5178Y) cells. (Table V)

TABLE V MCF-induced cytotoxicity against tumor targets Target MCF (units/ml) Crude MCF: K562 23.8 ± 9.1 HL-60 23.5 ± 1.5 partially purified MCF: K562  83.3 ± 12.3 L5178Y 78.4 ± 8.4 TU5 100.5 ± 26.8 Monocyte monolayers were activated with either crude MCF or MCF prepared over Matrex Gel Red A for 24 h before the addition of targets. Units were calculated as the reciprocal of the dilution giving 20% specific lysis. These are the results of 3 experiments run in quadruplicate.

TNF could not be demonstrated in supernatants collected from human monocytes incubated with 20 U/ml MCF for 20 h, washed and incubated for 24 h (dilution of 1:10). However, IL 1 was present at concentrations of up to 100 U/ml in MCF-activated mon(,cyte supernatant.

C. Response of MCF to Enzyme Treatment

In order to treat MCF supernatants with enzymes, 10 ml of the supernatant: (28.5 units/ml) were treated with 1 mg/ml trypsin at pH 7.4, 1 mg/ml chymotrypsin at pH 7.4, 0.5 mg/ml DNase at pH 7.4, cr 40 units/ml RNase at pH 5 for 1 hour at 25° C. The result of treating MCF with chymotrypsin was that there was a reduction in the biological activity of MCF by 54.4%. Trypsin, RNAse and DNAse had no significant effect. The experiments were repeated using insolubilized enzymes to minimize the possibility that enzymes could be carried over into the bioassay and could explain the results. However, the results were entirely comparable to those using soluble enzymes. Chymotrypsin reduced activity from 28.5 U/ml to 12.5 units, whereas trypsin RNAse and DNase treatment showed no significant differences after one hour of treatment, as measured by bioassay for MCF and determined by students T test.

D. Effects of Tunicamycin and Other Agents on MCF

Urea treatment was accomplished by adding 3 grams of solid urea to 10 ml MCF (28.5 U/ml) (5M urea final). Extraction of MCF with butanol-diisopropyl ether was performed. FtF3 cells were cultured with 0, 1, 2.5 or 5.0 ug/ml tunicamycin. Urea decreased biological activity in the MCF containing supernatants by 35.7%. MCF supernatants were extracted with butanol-diisopropyl ether; the aqueous phase contained 36.7% less MCF than the control preparation. Biosynthesis in the presence of either 2-mercaptoethanol or tunicamycin resulted in no significant change in biological activity of MCF.

E. Effects of Metabolic Inhibitors on MCF

FtF3 cells at a concentration of 1×10⁶/ml in RPMI 1640/10% FCS were incubated 4 hours with either actinomycin D, cycloheximide, or puromycin (all at 0 to 100 ug/mi, Sigma). Tests for viability after treatment were performed by trypan blue exclusion and supernatants were collected by centrifugation. In a second set of experiments FtF3 cells at the same concentration but using 0.1% human serum were incubated for 5 hours with either cycloheximide or puromycin. Uptake experiments were performed by adjusting FtF3 cells to 1×10⁶/ml in media after treatment with inhibitor, and adding either 5,6-³H-uridine (ICN Radiochemicals, Irvine, Calif., USA, 49, Ci/mmol) to actinomycin D treated cells or ³H L-amino acid mixture (25.5 mCi/mg) to cycloheximide-treated cells at 1 uci to 1×10⁵ cells. Cells were subsequently lysed and counted by liquid scintillation.

When MCF was grown in the presence of the metabolic inhibitors, actinomycin D totally suppressed production of MCF in a dose-dependent manner accompanied by a corresponding fall in ³H-uridine uptake. (FIG. 5) Cycloheximide suppressed but did not abolish MCF production. (FIG. 6) At intermediate doses (25 and 50 ug/ml) some escape from suppression was noted. Puromycin, like cycloheximide, suppressed but did not totally abolish MCF production under these conditions. (FIG. 7) A corresponding pattern was observed using tritiated amino acids and examining the pattern of incorporation in TCA insoluble material.

Actinomycin D had no effect, and cycloheximide had only a slight stimulatory effect, on MCF production of non-stimulated (non-PIRA treated) cells. Puromycin at doses of 10-50 ug/ml appeared to stimulate production of MCF by FtF3 cells not activated by lectin. Cycloheximide and puromycin therefore provide reversible inhibition. When inhibitor was present for the entire incubation period, lectin-induced MCF production is not suppressed by cycloheximide but puromycin was suppressive in a dose-dependent manner.

F. MCF Behavior in Other Bioassays

The biological activity of MCF was checked in other bioassays to probe the issue of multiple biologic activities. Supernatants from FtF3 containing 25 U/ml of MCF activity were substituted for IL 1 and IL 2 in their respective bioassays. MCF demonstrated no IL 1 or IL 2 activity. MCF had no TNF, M-CSF, or IFN-like antiviral biological activity when compared to RTNF, purified human m-CSF, IFN-gamma or alpha/beta respectively.

G. Physicochemical Characterization of MCF

1) pH Stability

pH stability of MCF was compared to IFN-gamma by dialyzing 40 U MCF or 100 U IFN-gamma in Spectropor tubing (molecular weight cutoff of 5×10³ Daltons) against 0.1 M glycine-HC1, pH 2.0, 0.1 M TRIS-HC1, pH 5.0, 0.15 M PBS, pH 7.4, 0.15 M PBS, pH 8.0, or 0.1M TRIS, pH 10.0 for 4 hrs at 25° C. The samples were then dialyzed against Dulbecco's PBS, pH 7.4, to restore neutrality prior to bioassay. IFN-garma was found to be totally inactivated at pH 2. However, as demonstrated by Table VI, MCF was found to be stable at pH 2. However, partial inactivation of MCF has consistently been noted at pH 8.0.

TABLE VI pH Stability of MCF pH % Specific Lysis 2 41.7 ± 8.6 5 41.1 ± 6.4 7.4 36.8 ± 3.2 8 19.6 ± 4.6 10 45.4 ± 5.4

2) Heat Stability of MCF

To test heat stability of MCF relative to IFN-gamma, 40 units of MCF and 100 U IFN-gamma in 1 ml RPMI 1640/1% FCS were heated for 2 hrs in a constant temperature bath to study heat denaturization. As demonstrated by Table VII, MCF was stable at temperatures up 60° C., but was totally inactivated at l00° C. IFN-gamma was not stable at temperatures higher than 4° C. for periods of 2 hrs or longer.

TABLE VII Heat Stability of MCF Temperature % Specific Lysis  4° 53.3 + 4.3  37° 48.6 + 4.9  60° 48.0 + 3.4 100° 0.0

7. Purification of MCF A. Gel Filtration of MCF

Gel filtration experiments were performed both to determine an approximate molecular weight and to begin preparation of a substantially purified fraction. 180 ml of MCF from PHA stimulated FtF3 supernatant (7.2×10³ U MCF) was concentrated 20-fold by pressure dialysis over an Amicon YM-10 membrane, applied to a 2.5×60 cm. column of Bio-Gel P100, equilibrated with PBS and eluted at a flow rate of 1.5 ml/min. 7.5 ml fractions were collected and were assayed undiluted, ½, and ⅕ for MCF activity. The column was calibrated with aldolase (158K), ovalbumin (45K), chymotrypsin (25K), and ribonuclease A (13.7K) (Pharmacia).

The data in FIG. 2 demonstrated that two peaks of biologic activity were obtained. The first peak co-eluted with the major protein present, bovine serum albumin (from the fetal calf serum present in the culture media). The second peak of monocyte cytotoxicity inducing activity eluted in a region with an apparent molecular weight of approximately 11,500 Daltons.

B. Precipitation with Ammonium Sulfate

Initially, ammonium sulfate precipitation was attempted as a method for purification and concentration. MCF appeared to precipitate in the 30-50% range but resulted in greater than an 85% loss in biologic activity. Therefore, ammonium sulfate precipitation was not pursued further as a means for purification.

C. Binding of MCF to Matrex Gel Resins

Two ml of each of the Matrex Gel Resins (Amicon) was washed with 5 M Urea and then washed with 20 ml PBS in 1.5 M NaCl, pH 7.4. Four ml of FtF3 supernatant (160 U MCF in RPMI 1640, 1%FCS) was passed twice over each of the Matrex Gel Resins (Blue A, Red A, Orange A, Green A, and Blue B), washed with 2 volumes of starting buffer, and eluted stepwise with 1 volume each 0.5M NaCl. 1.0M NaCl, and 2 volumes 1.011 NaCl/ 50% ethylene glycol. The starting material, wash, and each fraction was then dialyzed at 4° C. for 24 hrs (Spectrapor tubing, 5×10³ D molecular weight cut off) against 3 changes of PBS, pH 7.4, and then 4 hrs against distilled H₂O. The samples were placed in a glass tray and covered with Sephadex G-10 to reduce volume to approximately 1 ml. Each sample was then assayed for units MCF activity.

MCF was bound. and could not be eluted from Matrex Gels Orange A, Green A, and Blue B. However as summarized in FIG. 3, MCF bound to both Blue A, and Red A. Red A bound 31.3% of the starting material and eluted with 1.0M NaCl. Blue A bound only 10.5% of the starting and was not studied further. 175 ml of FtF3 supernatant/RPMI 1640, 1%FCS containing 7×10³ units MCF was passed twice over a 2.5×30 cm column Matrex Gel Red A. The column was washed with two column volumes of starting buffer and eluted in a single step with 1.0M NaCl. The peak activity was present in fractions 11-14. Two×10³ units in 20 ml (1.45 mg protein/iml) were collected. This preparative procedure resulted in a 2.5 fold concentration and gave a 28.5% yield. No IFN-gamma was detected in this preparation.

D. Polyacrylamide Gel Electrophoresis (SDS-PAGE)

To determine the molecular weight of MCF by an alternate procedure, samples having MCF activity were subjected to SDS-PAGE. In particular, 200 ul (20 U MCF/290 ug protein) prepared by chromatography over Matrex Gel Red A was mixed 1:1 with sample preparation buffer (0.0625 ml TRIS-HCl, 2% SDS, 5% 2ME, 10% sucrose, and 0.002% bromphenol blue), heated 3 min at 100° C., and centrifuged at high speed (1 min in an Adams microfuge). 100 ul aliquots were loaded into each of 4 lanes of a 1.5 mm thick SDS slab gel (BRL vertical gel apparatus, Gaithersburg, Md.) using a 10% polyacrylamide gel, prepared according to Laemmli (Nature, 227:680, 1970), and run at 90 V through the stacking gel and 200 V through the running gel. The gel was cut into 1 cm slices, crushed, and eluted with 2 washes of 5 ml of PBS/0.1% SDS pH 7.4, for 12 hrs at 4° C. The samples were placed in a glass dish, and covered with Sephadex G-10 to reduce sample volume to 1.5 ml. Pharmacia standards prepared in the same buffer and run in companion lanes were used to determine molecular weight; phosphorylase B (94K), bovine serum albumin (67K), ovalbumin (43K), carbonic anhydrase (30K), soybean trypsin inhibitor (20K), and alpha-lactalbumin (14.4K). A companion gel was divided and stained with 1) Coomasie Brilliant Blue and 2) by a silver nitrate method (Oakley et al., Anal. Biochem., 105:361, 1980).

Two peaks of MCF activity were obtained, one with a molecular weight between 78,400 and 63,600 Daltons which was associated with a major protein band, bovine serum albumin (specific activity 610 U MCF/mg protein), and a second peak between 18,100 and 14,700 (specific activity 1350 U MCF/mg protein) (FIG. 4). Using a silver stain method, a protein band was detected associated with the major peak of MCF activity at 14,700 Daltons, which could not be detected using Coomassie Brilliant Blue. Recovery of biologic activity from the gel was greater than 90%.

To determine the molecular weights of MCF prepared from the supernatants of cells grown in serum-free media, similar procedures were followed with some exceptions, e.g., 15% SDS-PAGE:, and the following low molecular weight standards: ovalbumin (43K), -chymotrypsinogen (25.7K), a-lactaglobulin (18.4K), lysozyme (14.3K), bovine trypsin inhibitor (6.2K), and insulin A or B chain, (2.3K and 3.4K). One half of the gel was sliced, crushed and eluted as previously described to determine biologic activity. A corresponding gel was washed briefly in distilled water and placed against 2 sheets of nitro-cellulose (Bio Rad, Richmond, Calif.) as described by Palade (Gershoni and Palade, Anal. Biochem. 124:396,1982); electroluted 4 hr at 200 mA using a Bio Rad Transblotapparatus in a Tris Glycine buffer, and stained with colloidal gold Aurodye (Anal. Biochem. 145:315, 1985). (FIG. 8A and 8B). Under serum-free conditions, the higher molcular weight species is found at 29 kilodaltons.

Treatment Protocols

Due to precautions which are necessarily attendant to every new pharmaceutical, due both to consideration of patient safety and federal new drug regulations, the MCF of the present invention has not been tested as yet in a clinical setting :Ln human subjects. However, the in vitro activity of MCF in stimulating monocytes to kill tumor cells, along with the recent clinical success of interleukin II, is believed to demonstrate the utility of the present invention in this regard. The following embodiments are therefore prophetic and represent the best mode contemplated by the present inventor of carrying out the practice of the invention in various clinical settings.

1. Antitumor Therapy A. Direct Infusion

It is believed that MCF will prove to be useful in the treatment of various tumors, and in particular, tumors of the blood forming organs such as leukemias, or solid tumors which have been described as infiltrated by machrophages, by way of direct intravenous infusion of pharmaceutical compositions which include MCF. Such compositions would include effective doses of either MCF alone, or in combination with other therapeutic agents such as interleulcin II, interferon, tumor necrosis factor or cytoxan. Interleukin II may be obtained as disclosed by numerous U.S. patents, including for example, U.S. Pat. Nos. 4,407,945 and 4,401,756, incorporated herein by reference. Cytoxan (cyclophosphamide) is a commercially available antineoplastic agent. Interferon is also commercially available as disclosed herein, and its clinical use has been reviewed and described in detail in numerous publications, including, for example, in Goldstein et al. (1986), Can. Res., 46:4325-4329, incorporated herein by reference. Moreover, Goldstein discloses in detail the suggested and reported dose regimens for interferon antitumor therapy. Preparation of Tumor Necrosis Factor and its use is known in the art as exemplified by U.S. Pat. Nos 4,457,916; 4,529,594; and 4,447,355 and as further disclosed by Carswell et al. (1975), Proc. Natl. Acad. Sci, USA, 72: 3666; Ruff et al. (1980), J. Immunol., 125: 1671; Matthews et al. (1980), Br. J. Cancer, 42: 416; and Lu et al. (1986), Cancer Res., 46(9): 4357, all of the foregoing references being incorporated by reference. Therefore, it is considered that use and dosages of MCF treatment, alone or in combination with these agents, is well within the skill of the art in light of the present specification.

MCF could be given daily by continuous infusion or given on alternative days with interleukin-2 or interferon being given on the other day. Such a treatment would be possible since the cytotoxic effect of MCF seems to last for about approximately 24 hours. Alternatively a large initial dose of Cytoxan could be given which should deplete suppressor T-lymphocytes followed by continuous infusion of MCF. Doses of MCF would of course have to be determined by experimental methods which are well known to skilled immunologists. However, dosages will likely be at least an order of magnitude lower than dosages of interferon gamma Interferons are usually given as an IM dose of 3 million units thrice weekly although one would have to take into account whether total body water is being saturated. With a new agent of any type one would have to initiate a phase I trial first to establish levels at which unacceptable toxicity is reached.

B. Adoptive Immunotherapy

Adoptive immunotherapy is a new approach to treating metastatic cancer in which immune cells with antitumor reactivity are transferred to the tumor-bearing patient. Much of this work has been pioneered by Dr. Steven Rosenberg and is discussed in more detail in Resenberg et al. (1977), Adv. lancer Res., 25:323 and Rosenberg (1984), Cancer Treat. Rep., 68:233, both incorporated by reference. In particular, interleukin II, also referred to as T-cell growth factor, has been shown to be a useful adjuvant to adoptive immunotherapy, wherein it is used to stimulate killer 97-cell development (see, e.g., Rosenberg (1985), J. Natl. Cancer Inst., 75:595, incorporated herein by reference). Moreover, adoptive therapy utilizing interleukin II has; demonstrated applicability in the treatment of a variety of advanced metastatic cancers in humans (Rosenberg et al. (1985), N. Eng. J. Med., 313:1485, incorporated herein by reference).

Accordingly, it is submitted that the MCF of the present inventions can be utilized in an adoptive immunotherapy protocol in a manner similar to interleukin II. In particular, it is believed that the following proposed protocol will serve as a sufficient basis to teach those skilled in the art of adoptive immunotherapy to utilize MCF in this manner.

Monocytes will be harvested by cell separation using, for example, an IBM cell separator using accepted techniques. These cells would then be incubated with approximately 4 units/ml of MCF overnight followed by slow continuous infusion of the induced cells into the patients. Such therapy could initially be given 2 to 3 times a week. However, because of the long life span of monocytes it could perhaps be given at more infrequent intervals stretched over a much longer period to time to insure that infiltration into the tumor occurs.

C. Diagnostic Utility

MCF will additionally be of value as a clinical diagnostic aid. For example, antibodies having specificity for MCF will provide an ability to determine MCF blood levels, thereby assisting in maintaining therapeutic blood levels and perhaps in the diagnosis of T-cell malignancies which may be accompanied by high serum MCF levels. Moreover, MCF antiserum may be of use in evaluating T-cell function in normal individuals. Similar uses have been described for the so-called melanoma-associated antigen.

The development of antibodies to a particular antigen whether polyclonal or monoclonal, are well known in the art and can readily be achieved by skilled immunologists. This is the case even where the particular molecule is not antigenic in and of itself, through either the attachment of an immunostimulating ligand such as keyhole limpet haemocyanin, or by finding a species wherein the molecule is antigenic.

In the case of MCF it is believed that an antibody can readily be developed by either a polyclonal or monoclonal approach. For example, rabbits should be immunized with 100 micrograms of MCF in complete Freund's adjuvant into each of four sites and later boosted with MCF in incomplete Freund's adjuvant. Once a hetero-antisera has been developed and quantitation determined by immunodot assay, western blotting, ELISA and various other immunodiagnostic techniques may be performed with such a hetero-antiserum. Monoclonal antibodies may be developed by a number of accepted techniques, for example, as disclosed by U.S. Pat. Nos. 4,172,124 and 4,271,145, both to Koprowski et al., incorporated herein by reference.

For in vitro diagnostic work, for example, in an immunoassay to quantitate serum MCF levels, the MCF antibody will be used most preferably in an ELISA assay which employs the antibody together with an immuno detection reagent capable of detecting quantitatively specific immune complex formation.

However, in general, immunodiagnostic kits would include reagents appropriate for either detecting patient-generated anti-MCF antibodies (e.g. circulating antibodies) or detecting MCF, for example, tumor-generated MCF, in biologic fluids or tissues from patients. As used herein, a biologic fluid or tissue includes any fluid or tissue obtained from a patient, including, for example, urine, serum, plasma, and biopsy samples. In the case of MCF antibody-detection kits, such kits would include antigenically pure, and preferably titrated, MCF together with an immunodetection reagent. By antigenically pure MCF is meant an MCF preparation which does not substantially cross-react with non-MCF directed antibodies. Sufficient antigenic purification could be achieved through immunopurification by adsorption with normal sera or chromatography over anti-MCF antibodies as is known in the art.

In the case of MCF antigen detection kits, such kits would typically include antigenically pure, preferably titrated, anti-MCF antibody. By antigenically pure is meant antibody which will not substantially cross-react with antigens other than MCF. As with MCF antigen purification, polyclonal antibody purification could be achieved by immuno chromatography. However, a preferred antibody would be a monoclonal antibody.

In either case, immunodetection kits would include an immunodetection reagent for detecting and/or quantifying the occurrence of specific immunoreactions involving MCF. Typically such reagents include, for example, a radioactive or enzyme-linked ligand. Such ligands are typically associated with either the antibody, antigen or a second antigen or antibody. As noted, a preferred immunodetection system are the various systems based on the ELISA assay. For a further description of the ELISA assay and the various immunodetection reagents, please refer to U.S. Pat. Nos. 4,454,233 and 4,446,232, both incorporated herein by reference. It is believed that these patents provide sufficient disclosure to enable the use of antibody to MCF in a clinical immunoassay.

The present invention has been disclosed in terms of specific embodiments which are believed by the inventor to be the best modes for carrying out the invention. However, in light of the disclosure hereby provided, those of skill in the various arts will recognize that modifications can be made without departing from the intended scope of the invention. For example, although the present invention is disclosed in terms of a Sezary cell hybridoma for MCF production, it is clear that other types of T-cells may be employed. Additionally, numerous embodiments are likely possible for isolation of the factor. Moreover, as biological characterization of the factor progresses, it is likely that more refined and simpler assays will be developed for MCF identification. For example, once an antibody to MCF has been developed, such antibody can be used directly to assay for MCF production by the various cell populations. These and all other modifications and embodiments are intended to be within the spirit and scope of the present invention and appended claims. 

What is claimed is:
 1. A method of generating a continuous cell line which produces a factor capable of inducing human monocytes to a cytotoxic state, the method comprising the steps of: (a) immortalizing human T-cells to produce continuous cell clones; (b) identifying a clone which produces a factor having the following characteristics: i. capability of inducing human monocytes to a cytotoxic state; ii. retention of biological activity following treatment at pH 2 for one hour; iii. retention of biological activity following treatment at 60° C. for one hour; iv. ability to bind to Matrex Gel Red A under low-salt conditions and elute from Matrex Gel Red A under high-salt conditions; and v. retention of biological activity in the presence of anti-serum to interferon gamma, interferon alpha, or a combination of anti-sera to interferon alpha and gamma; and (c) culturing the clone to produce the continuous cell line.
 2. The method of claim 1, wherein the factor produced by the clone exhibits an apparent molecular weight of between about 14.7 and 18.1 kilodaltons upon SDS-polyacrylamide gel electrophoresis.
 3. The method of claim 1, wherein step (a) comprises fusing a T-cell population with a second cell population conditioned to grow continuously in tissue culture, wherein the second cell population is capable of growth in a selective media; and culturing the fused cells in the selective media to produce the continuous cell clones.
 4. The method of claim 3, wherein the second cell population is a T-cell lymphoma.
 5. The method of claim 1, wherein the T-cell population is a Sezary cell population.
 6. The method of claim 1, wherein the T-cell population is an effector T-cell population.
 7. The method of claim 1, wherein step (b) comprises the steps of: (a) stimulating the clone with a T-cell mitogen to release lymphokines; (b) culturing human monocytes together with appropriate target cells in the presence of the released lymphokines; and (c) detecting target cell lysis wherein such lysis is indicative of the presence of human monocyte cytotoxicity inducing factor in the released lymphokines.
 8. A continuous cell line producing a human monocyte cytotoxicity inducing factor, the factor characterized by the following properties: (a) capability of inducing human monocytes to a cytotoxic state; (b) retention of biological activity following treatment at pH 2 for one hour; (c) retention of biological activity following treatment at 60° C. for one hour; (d) ability to bind to Matrex Gel Red A under low-salt conditions and elute from Matrex Gel Red A under high-salt conditions; and (e) retention of biological activity in the presence of anti-serum to interferon gamma, interferon alpha, or a combination of anti-sera to interferon alpha and gamma.
 9. The cell line of claim 8, wherein the factor exhibits an apparent molecular weight of between about 14.7 and 18.1 kilodaltons upon SDS-polyacrylamide gel electrophoresis.
 10. A continuous cell line which produces a factor capable of inducing human monocytes to a cytotoxic state, the continuous cell line being produced by a process comprising the steps of: (a) immortalizing human T-cells to produce continuous cell clone; (b) identifying a clone which produces a human monocyte cytotoxicity inducing factor having the following properties: i) capability of inducing human monocytes to a cytotoxic: state; ii) retention of biological activity following treatment at pH 2 for one hour; iii) retention of biological activity following treatment at 60° C. for one hour; iv) ability to bind to Matrex Gel Red A under low-salt conditions and elute from Matrex Gel Red A under high-salt conditions; and v) retention of biological activity in the presence of anti-serum to interferon gamma, interferon alpha, or a combination of anti-sera to interferon alpha and gamma; and (c) culturing the clone to produce the continuous cell line.
 11. The cell line of claim 10, wherein the factor produced by the clone exhibits an apparent molecular weight of between about 14.7 and 18.1 kilodaltons upon SDS-polyacrylamide gel electrophoresis.
 12. The cell line of claim 10, wherein step (a) comprises fusing human T-cells with a second cell population conditioned to grow continuously in tissue culture wherein the second cell population i-s sensitive to growth in a selective media; and culturing the fused cells in the selective media to produce the continuous cell clones.
 13. The cell line of claim 10, wherein the T-cells are further defined as Sezary cells.
 14. The cell line of claim 10, wherein the T-cells are further defined as helper T-cells.
 15. The cell line of claim 10, wherein step (b) comprises the steps of: (a) stimulating the clone with a T-cell mitogen to release lymphokines; (b) culturing human monocytes together with appropriate target cells in the presence of the released lymphokines; and (c) detecting target cell lysis, wherein such lysis is indicative of the presence of a human monocyte cytotoxicity inducing factor in the released lymphokines.
 16. A Sezary cell hybridoma line which secretes a monocyte cytotoxicity inducing factor characterized by the following properties: (a) capability of inducing human monocytes to a cytotoxic state; (b) retention of biological activity following treatment at pH 2 for one hour; (c) retention of biological activity following treatment at 60° C. for one hour; (d) ability to bind to Matrex Gel Red A under low-salt conditions and elute from Matrex Gel Red A under high-salt conditions; and (e) retention of biological activity in the presence of anti-serum to interferon gamma, interferon alpha, or a combination of anti-sera to interferon alpha and gamma.
 17. The Sezary cell hybridoma line of claim 16, wherein the factor exhibits an apparent molecular weight of between about 14.7 and 18.1 kilodaltons upon SDS-polyacrylamide gell electrophoresis.
 18. The Sezary cell hybridoma line of claim 16, produced by a process which includes: (a) fusing a Sezary cell population with a second cell population conditioned to grow continuously in tissue culture wherein the second cell population is sensitive to growth in a selective media; (b) culturing the fused cells in the selective media to produce Sezary cell hybridoma clones; (c) identifying a clone which secretes the human monocyte cytotoxicity factor; and (d) culturing the :lone to produce the hybridoma line.
 19. The hybridoma, line of claim 18, wherein the second cell population is a T-cell lymphoma. 